I am wondering if you have considered adding any sort of tag bundling/nesting/hierarchical organization feature? I have found this very helpful on other bookmarking sites such as Pinboard, and would be thrilled if this feature were rolled out at some point in the future. I have many thousands of tags on my bookmarks and find it helpful to be able to group, for example, my tags for the author of the work vs. my tags for media it is related to vs. my tags for length of article.